Prime Minister Binali Yildirim has claimed victory for the 'Yes' vote in the referendum to amend Turkey's constitution.

Prime Minister Binali Yildirim has claimed victory for the "Yes" vote in the referendum to amend Turkey's constitution and grant the presidential office new executive powers.

As of 18:00GMT on Sunday, the “Yes” campaign was leading with 51.2 percent to 48.8 percent with 98.4 percent of votes counted.

"I am grateful to everyone who made the effort to go to the ballot box in the name of democracy," said Yildirim.

The proposed changes transform Turkey's governance from a parliamentary system to an executive presidency, significantly expanding the powers of the top office.

The changes were backed by the governing Justice and Development Party (AK Party), founded by President Recep Tayyip Erdogan, and the leadership of the Nationalist Action Party (MHP), whose parliamentary support was vital to take the amendments to a public vote.

The main opposition Republican People's Party (CHP), the pro-Kurdish People's Democracy Party (HDP) and other critics argue the amendments give too much power to one individual, undermining the separation of powers in the government.

The constitutional changes will only enter into force after the presidential and parliamentary elections set for 2019. Erdogan will have to be elected then to claim the powers this referendum brings.

This result gives the president new powers to assign ministers, high-level state officials, and vice-presidents, as well as half the members in the country's highest judicial body.

It will also allow the president to dissolve parliament, and issue executive decrees and state of emergencies.